Context: Imagine a sequence of indices greater than 1. The sequence must follow these rules:
1.) Index 2 cannot be surrounded by two indices 3.
(I know this may be written in much more simple way, but the structure should remain the same.)
The question: in the beginning of the first rule, should there be any article before the word "Index" (like: The index 2... / An index 2...) or is it also correct without any article?
Is "Index 2" in this context definite or not? (there may be more indices 2 in the sequence and the rule should apply to all of them)